Combination-cell foam floating island

ABSTRACT

A floating island comprising a combination-cell thermoplastic foam. In a preferred embodiment, the invention is a floating island comprising: an island body comprising at least a first portion that comprises a combination-cell thermoplastic foam and having a cavity; and a bedding material that is disposed in said cavity; wherein said combination-cell thermoplastic foam is buoyant in water and permeable to gas and water. In another embodiment, the invention is a floating island comprising: an island body comprising a first matrix layer, a second matrix layer and a third matrix layer; and a gas-trapping insert that is disposed between two of said layers.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/631,833 filed on Dec. 6, 2009. The contents of that application areincorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to floating islands. In particular, the inventionrelates to combination-cell foam floating islands.

The background art is characterized by U.S. Pat. Nos. 5,224,292;5,528,856; 5,766,474; 5,980,738; 6,086,755; and 6,555,219 and U.S.Patent Application Nos. 2003/0051398; 2003/0208954; 2005/0183331; thedisclosures of which patents and patent applications are incorporated byreference as if fully set forth herein.

Background art floating planters have four major deficiencies that areovercome in preferred embodiments of the present invention. Somebackground art planters are predominantly covered by materials thatprevent or restrict plant growth. For example, the invention describedby Tepper (U.S. Pat. No. 6,086,755) comprises a top floatation layerthat is manufactured from a conventional buoyant foam such as a foamedplastic. This material is not suitable for plant growth; therefore, thisinvention requires cutouts to be installed through the foam layer, andplants can only grow through the cutouts. With the Tepper invention,only a portion of the top surface area of the planter is available forplant growth, which reduces the total plant growing capacity of thestructure.

Other background art planters use hollow buoyant pipes that areinstalled around the perimeter of the structure to provide buoyancy. Forexample, Waterlines Solutions of the U.K. utilizes sealed polypropylenetubes around the perimeter of its floating planters to provide buoyancy.This method of providing buoyancy tends to be fragile (e.g., subject tofailure by impact from boats and pressure from freezing ice) andexpensive.

BRIEF SUMMARY OF THE INVENTION

The purpose of the invention is to provide an economical floatingisland. Some embodiments of the invention comprise a material(combination-cell thermoplastic foam) that has not been used in thebackground art. This material has several beneficial properties thatrequire the use of multiple materials in the background art. Thematerial provides buoyancy via the closed cells, water wicking and wateradsorption via the open cells; it is penetrable by plant roots andresistant to chemical and sunlight degradation. When used under pocketsof bedding soil, it prevents loss of soil while supporting root growthand providing buoyancy. The formulation of the combination-cell foam canbe varied so as to produce a variety of foam products from the sameresin stock, thereby reducing manufacturing costs.

Some embodiments of the invention are specifically designed to maximizethe use of scrap materials, thereby reducing production costs and alsoconverting waste products into environmentally beneficial products.Fastening devices have been improved over the background art to be moreeconomical, stronger, and more efficient.

Utilization of combination open/close celled foam as a comprehensiveone-material floating island solution allows for simplified, lessexpensive mass production. This, in combination with features likeenhanced ultraviolet (UV) light protection, provides for a higherquality, more consistent product.

In summary, this disclosure describes improvements to the background artfloating island technology embodied in products manufactured by FloatingIsland International, LLC, of Shepherd, Mont. The improvements describedin this disclosure result in lower production costs for floating islandproducts that perform as well or better than background art productionmodels. The improvements include changes in construction materials andfabrication methods.

In a preferred embodiment, inexpensive and durable floating (buoyant)islands are made by replacing background art thermosetting (e.g.,polyurethane) foam with thermoplastic (e.g., polypropylene,polyethylene, or ethylene vinyl acetate) foam. In preferred embodiments,the thermoplastic foam is comprised of a combination of open and closedcells, which provide benefits that are not present in foams that arecomprised of either open cells alone or closed cells alone.Thermoplastic foams that contain both open and closed cells arepreferably produced by an extrusion process that is similar to the onesused to produce both open cell foam and closed cell foam. By adjustingthe manufacturing conditions such as foaming gas injection volume,extrusion temperature, and extrusion pressure, a portion of the gasbubbles break as they expand within the curing polymer, therebyproducing open cells. The remaining portion of the gas bubbles remainintact as they expand, thereby producing closed cells. An example of amanufacturer of this “combination-cell” material is Nomaco Corporationof Zebulon, N.C. The open cells can absorb and wick water, and theyallow easy penetration by plant roots and stems. The closed cells aregas-filled, thereby reducing the total weight of the sheet, andproviding buoyancy when the material is submerged. The ability toinclude open and close cells in the same material at whatever ratio isdesired eliminates several manufacturing operations that would otherwisebe required to achieve a desired buoyancy in combination with anappropriate gas and water exchange rate within the body of a floatingisland.

In another preferred embodiment, the growth medium is contained by anunderlayer of permeable foam sheeting. The sheeting is preferablycomprised of thermoplastic (e.g., polypropylene, polyethylene, orethylene vinyl acetate) foam. The pore spaces comprising thethermoplastic foam comprise a combination of open and closed cells.

In another preferred embodiment, the buoyancy and outer coveringmaterials are rendered more resistant to degradation by sunlight andother environmental effects by the utilization of inert thermoplasticmaterials. In this embodiment, the buoyancy and outer covering materialsare comprised of thermoplastic or thermoplastic foam. Both of thesematerials are relatively inert compared to other materials, such asthermosetting polymers. Inert materials do not react chemically withreactive materials such as water or petroleum products; therefore, theydo not degrade when exposed to these materials. In addition,thermoplastic materials are generally more resistant to sunlight-causeddegradation than thermosetting materials.

In another preferred embodiment, the entire island body is comprised ofcombination-cell thermoplastic foam. This embodiment is both buoyant andpenetrable by plants.

In another preferred embodiment, the capillary wicking tubes of previousembodiments have been made more effective and less expensive byutilizing novel, pre-manufactured wicking cups filled with wickinggrowth medium.

In yet another preferred embodiment, the matrix is rendered self-buoyantand more durable by incorporating thermoplastic polymer shapes (shapesmay include threads, rods, strands, tubes, strips, etc.) orthermoplastic polymer foam shapes. The shapes are preferably melted orbonded together with a binder to form a matrix. Thermoplastic foams mayalternately be used in place of polyurethane foam to provide adhesionbetween matrix layers and/or buoyancy for the island. These shapes arepreferably produced by an extrusion process, wherein plastic pellets aresoftened by increasing temperature and shear forces within a mechanicalextruder. An expansion gas such as compressed iso-butane is injectedinto the softened plastic within the extruder. The softened plasticexits the extruder in a continuous stream through a nozzle. As theplastic exits the nozzle, the gas within the plastic expands and formsbubbles, producing closed cell foam. The foam cools sufficiently to setwithin a few seconds after exiting the nozzle. Although extrusionmachines typically produce a continuous outlet stream, individual“shots” of foam may be produced by means of a shuttle valve thatalternately shunts the stream of soft plastic back and forth between twoor more outlets.

In another preferred embodiment, internal buoyancy is integrated withinthe island body by extruding uncured thermoplastic foam into the porousmatrix. Examples of suitable thermoplastic foams include polyethylene,polypropylene and polyester foams. In this embodiment, the thermoplasticmaterial expands and sets around at least some of the fibers of thematrix to form a volume of non-permeable closed cell foam within theisland body. The density of the thermoplastic foam may be adjusted byvarying the chemical formula of the resin, or by varying the applicationparameters such as the volume of expansion gas, the extrudertemperature, and the extrusion rate. Practical densities of curedthermoplastic foam for the islands range from about 0.5 to about 25.0pcf. By selecting a thermoplastic resin that has a lower meltingtemperature than the polyester fibers of the matrix, the moltenthermoplastic foam can be injected into the matrix without melting thepolyester fibers. For example, a molten polyethylene foam at atemperature of 110 degrees C. can be injected into a polyester matrixthat has a melting point of 150 degrees C.

In yet another preferred embodiment, uncured thermoplastic foam iscontinuously extruded onto a continuous layer of matrix that passes infront of the thermoplastic extrusion nozzle on a moving production line.The thermoplastic foam expands and sets to form a continuous strip ofbuoyant foam that is bonded to the matrix. The lengths of foamed matrixbodies are preferably cut into individual island shapes in a subsequentmanufacturing operation. Optionally, two or more layers of matrix may bestacked with uncured foam introduced between them during the productionoperation, resulting in a multi-layer matrix with foam between thelayers after the foam cures. In this configuration, the foam providesadhesion between joining layers as well as buoyancy.

In a further preferred embodiment, holes or strips are precut into thematrix, and molten thermoplastic foam is extruded into the precut voids,where it expands and sets. This technique may be preferred in caseswhere injecting the molten foam directly into the matrix results in poorquality foam due to the matrix fibers causing the foam bubbles to breakduring the expansion process, which could result in a less preferredfoam that absorbs water and loses buoyancy.

In another preferred embodiment, pre-manufactured thermoplastic foamcylinders or other prismatic shapes are installed into precutcylindrical or other holes within the matrix, where they are retained byeither a friction fit, or by melting, or via a mechanical pin device. Inyet another preferred embodiment, pre-manufactured lengths of extrudedfoam rods or “noodles” are laid lengthwise between multiple layers ofmatrix, and the assembly is bonded by melting or by means of an adhesiveor an adhesive foam or a mechanical pin device to form a “sandwich” withinternal buoyancy provided by the foam noodles.

In another preferred embodiment, relatively small diameter foam noodlesare pre-manufactured, and then used to form a buoyant matrix by bondingthe noodles together via controlled melting, or by applying suitableadhesive such as latex binder, or by mechanically tangling the fibers toform a nonwoven blanket, or by weaving the fibers to form a wovenblanket or by use of an adhesive foam, like polyurethane. Islands madefrom the buoyant matrix of this embodiment require less additionalbuoyancy in the form of discrete pieces of buoyant foam, and may beadequately buoyant for some island applications without any additionalbuoyancy components. The minimum diameter of commercially availablenoodles is approximately ¼-inch, but smaller diameter noodles (e.g.,0.05 inch) are technically feasible and may be preferred for makingbuoyant matrix. One example of a manufacturer of ¼-inch diameterpolyethylene foam rods is Nomaco Corporation of Zebulon, N.C.

Buoyancy tests preformed by the applicants indicate that matrix madefrom ethylene vinyl acetate and polypropylene (without binder additives)is buoyant, while matrix made from polyester fibers with latex binder isnot buoyant. Thus, nonwoven matrix made by melting the fibers togetheris buoyant; nonwoven matrix made with latex binder is not buoyant. Ifthe fibers are made of foamed polymer, then the matrix is more buoyantthan if it is made with the same material that is not foamed.

In another preferred embodiment, an inexpensive means is used to joinbuoyant units to the matrix. The inexpensive means preferablyincorporates novel mechanical fastening pins.

Furthermore, modular units may be joined laterally or vertically byinexpensive mechanical fasteners, thereby providing a means for astandard-size product to be modified to any desired thickness and/orsurface area.

In yet another preferred embodiment, scrap materials (both thermoplasticand thermosetting materials) are incorporated into the island body,thereby reducing costs and providing environmental benefits. This can beachieved by putting irregular shapes of scrap matrix or foam of anypolymer type into a predetermined shape and either bonding with theadhesive means previously described, or sandwiching the scrap betweennon scrap sheets of nonwoven matrix, or alternatively, by passing scrapthrough a mechanical device, like a wood chipper, and producing ahomogenous material characterized by a high level of surface area. Thismaterial is then used as a filler within predetermined island moduleshapes. Alternatively, this material can be baled much like straw orhay. Depending on the level of buoyant polymer that makes up thehomogenous mix, such bales may be appropriately buoyant, or may requireadded levels of buoyancy.

In another preferred embodiment, wicking and buoyancy are incorporatedinto a single (e.g., thermoplastic) material that comprises acombination of open and closed cells, thereby reducing both material andconstruction costs, while improving floating island efficiency.

The buoyant foam that provides adhesion between layers as well asbuoyancy for the structure is preferably comprised of an inertthermoplastic polymer, thereby reducing material costs and improvingdurability. In a first embodiment, conventional thermosettingpolyurethane foam is used to bond the top, bottom, and sides of thematrix together, and closed cell or combination-cell thermoplastic foam(optionally, scrap foam) is used as a filler in the interior islandspace to provide inexpensive buoyancy for the floating island. In asecond embodiment, thermoplastic foam is used exclusively to provideboth adhesion and buoyancy for the floating island. If combination-cellthermoplastic foam is used, then plant roots can penetrate it.

A single type of material (thermoplastic foam) is preferably used forseveral purposes on a floating island, by varying the volumes and ratioof the open and closed cells that are produced during the extrusion ofthe foam material, thereby reducing material costs. For applications inwhich the primary objective is to maximize long-term buoyancy and rootpenetration is not required (e.g., injected buoyant units), then closedcell foam is preferred. Closed cell foam does not absorb water, and ithas the most preferred long-term durability of thermoplastic foamvarieties. For applications where wicking and water absorption are theprimary objectives and buoyancy is not important (e.g., as a growthmedium additive), open-cell foam is acceptable and may be less expensiveto obtain than other foam types. For applications where wicking,buoyancy and root penetration are required (e.g., for submerged wickingcups), the combination-cell foam that contains a mixture of open andclosed cells is preferred. The same thermoplastic resin stock may beused to produce all three varieties of foam.

Gas-impermeable inserts of various shapes (e.g., sheet or saucer-shaped)may be manufactured into the floating island body below waterline. Theseinserts trap gases on their undersides, thereby providing renewable,long-term buoyancy to the island.

In a preferred embodiment, the floating islands are manufactured so asto provide both aerobic and anaerobic zones within the same island. Thisrenders the floating islands useful for a wide range of biologicalremediation applications.

By incorporating closed cell foam scrap within the body of a floatingisland, three objects are accomplished: more buoyancy, trapped gas atrandom within the island, and the creation of zones that can allow gasand water passage. This multiplicity of aerobic and anaerobic zonesstill allows for water to filter through the island, exposing aerobicand anaerobic microbes to various nutrients within the water. Applicantshave learned that scrap foam and/or scrap or commercial qualitycombination open/close cell foam may be used at specific ratios andachieve the blend of buoyancy (based on close cell foam) withfiltration, (based on open cell foam) to provide both buoyancy andappropriate filtration, inexpensively.

The required percentage of closed cell foam for an island is determinedby the buoyancy requirements for the island. The closed cells within thefoam are filled with trapped gas, and therefore provide buoyancy whensubmerged. Open cells within the foam become saturated with water whensubmerged, and do not provide buoyancy. For example, consider an islandthat is one foot thick, and having a foam component that is required toprovide a buoyancy of 10 pounds per square foot of island surface area.Lightweight foam that is comprised entirely of closed cells providesabout 60 pounds of buoyancy per cubic foot (pcf) of foam; therefore, 10pounds of buoyancy will require about (10 lb./60 pcf)=0.17 cubic foot ofclosed cell foam per cubic foot of island matrix. In other words, thematrix must comprise 17% closed cell foam by volume. However, if thefoam is combination-cell foam that is comprised of cells that are 50%closed and 50% open, then the matrix must contain twice as muchcombination-cell foam by volume (2×17%=34%) to achieve the requiredbuoyancy of 10 pounds per square foot of island surface area, becausethe buoyancy is only provided by the closed-cell fraction of total cellswithin the foam. Similar calculations can be made for any combination ofisland thickness, desired buoyancy, and foam.

Gas impermeable inserts, in addition to being buoyant, may be shaped(e.g., in an upside down saucer shape) to trap bio-gas or otherintroduced gas underneath them, providing another low-cost buoyancyfeature. All of these inexpensive buoyancy improvements reduce the needto rely on polyurethane, an expensive and potentially hazardousmaterial. Instead of utilizing polyurethane for both buoyancy andadhesion, it can be used more sparingly, if at all.

In a preferred embodiment, the invention is a floating islandcomprising: an island body comprising a nonwoven plastic fiber matrix,said island body having a central cavity and a bottom having a pluralityof holes; a shaped liner having a plurality of liner holes; a pluralityof wicking cups that connect each said hole to each side liner hole,each said wicking cup having an outer layer and a central portion; and agrowth medium that is disposed in said shaped liner and in each saidcentral portion. Preferably, said island body is comprised of a nonwoventhermosetting or thermoplastic fiber matrix. Preferably, said growthmedium is a wicking composition. Preferably, said growth mediumcomprises a hydrophilic polymer foam and a plurality of organicmaterials. Preferably, said outer layer comprises a combination-cellfoam. Preferably, said shaped liner comprises a combination-cell foam.

In another preferred embodiment, the invention is a floating islandcomprising: an island body comprising at least a first portion thatcomprises a combination-cell thermoplastic foam and having a cavity; anda bedding material that is disposed in said cavity; wherein saidcombination-cell thermoplastic foam is buoyant in water and permeable togas and water. Preferably, the floating island further comprises: asecond portion that comprises a matrix.

In yet another preferred embodiment, the invention is a floating islandcomprising: a buoyant matrix layer comprising a combination-cellthermoplastic foam; a grass sod layer that is disposed on said buoyantmatrix material. Preferably, the floating island further comprises: anonwoven matrix layer that underlies said buoyant matrix material.Preferably, said buoyant matrix layer is selected from the groupconsisting of: a thermoplastic polymer shape, a thermoplastic polymerfoam shape, and a combination of the shapes.

In a further preferred embodiment, the invention is a fastening assemblycomprising: at least two fastening pins, each of said fastening pinscomprising a substantially U-shaped, stiff body having legs havingnotches; and a connecting cable that connects said fastening pins. Inanother preferred embodiment, the invention is a fastening unitcomprising: a substantially U-shaped, stiff, planar body having asubstantially flat top and legs having notches.

In another preferred embodiment, the invention is a combinationcomprising: a first floating island with an island body comprising afirst combination-cell thermoplastic foam portion and a first matrixportion; a second floating island comprising a second combination-cellthermoplastic foam portion and a second matrix portion; and a fasteningunit disclosed herein wherein one fastening pin is embedded in saidfirst matrix portion and a second fastening pin is embedded in saidsecond matrix portion.

In another preferred embodiment, the invention is a combinationcomprising: a buoyant matrix layer comprising a combination-cellthermoplastic foam; a grass sod layer that is disposed on said buoyantmatrix material; a nonwoven matrix layer that underlies said buoyantmatrix material; and a fastening unit disclosed herein embedded in atleast two of said layers.

In another preferred embodiment, the invention is a floating islandcomprising: an island body that comprises a first combination-cellthermoplastic foam portion and having a cavity; a bedding material thatis disposed in said cavity; a top cover that comprises a secondcombination-cell thermoplastic foam portion that is disposed on saidisland body; wherein said combination-cell thermoplastic foam portionsare buoyant in water and permeable to gas and water.

In another preferred embodiment, the invention is a floating islandcomprising: an island body comprising a matrix top, a matrix bottom andmatrix sides and having an interior portion; and a scrap material thatis disposed in said interior portion, said scrap material comprising acombination-cell thermoplastic foam portion; wherein saidcombination-cell thermoplastic foam portion is buoyant in water andpermeable to gas and water.

In yet another preferred embodiment, the invention is a floating islandcomprising: an island body comprising a first matrix layer, a secondmatrix layer and a third matrix layer; and a gas-trapping insert that isdisposed between two of said layers, said gas-trapping insert beingfabricated from a material selected from the group consisting of acombination-cell thermoplastic foam and a solid thermoplastic; whereinsaid combination-cell thermoplastic foam portion is buoyant in water andpermeable to gas and water.

Further aspects of the invention will become apparent from considerationof the drawings and the ensuing description of preferred embodiments ofthe invention. A person skilled in the art will realize that otherembodiments of the invention are possible and that the details of theinvention can be modified in a number of respects, all without departingfrom the concept. Thus, the following drawings and description are to beregarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The features of the invention will be better understood by reference tothe accompanying drawings which illustrate presently preferredembodiments of the invention.

FIG. 1 is an exploded perspective view of a preferred embodiment of theinvention that comprises wicking cups and a shaped liner for preventingthe loss of growth medium.

FIG. 2 is a side cross-section view of the embodiment of FIG. 1, afterthe island parts have been assembled and plants have become established.

FIG. 3 is a side cross-section view of another embodiment of a floatingisland that comprises lost-cost materials.

FIG. 4 shows a side cross-section view of another low-cost embodiment ofa floating island in which the island body is comprised entirely ofthermoplastic foam.

FIG. 5 is a side cross-section view of yet another low-cost embodimentof a floating island.

FIG. 6 is a perspective view of a preferred embodiment of a fasteningassembly.

FIG. 7 is a perspective view of a preferred embodiment of a fasteningassembly.

FIG. 8 is a side cross-section view of an embodiment of a floatingisland that comprises a thermoplastic foam top cover, in which thethermoplastic foam is comprised of both open and closed cells.

FIG. 9 is a side cross-section view of a preferred embodiment of afloating island that is comprised of a significant percentage of scrapmaterial.

FIG. 10 is a side cross-section view of preferred embodiment of afloating island having gas-trapping inserts.

The following reference numerals are used to indicate the parts andenvironment of the invention on the drawings:

-   -   1 island body    -   2 wicking cups    -   3 shaped liner    -   4 matrix    -   5 central cavity    -   6 cutout holes    -   7 outer layer    -   8 central portion    -   9 growth medium    -   10 plants    -   11 roots    -   12 water body    -   13 thermoplastic foam    -   14 bedding mix    -   17 grass sod layer, sod layer    -   18 buoyant matrix material, buoyant matrix layer    -   19 coarse nonwoven matrix material    -   20 fastening assembly    -   21 fastening pins    -   22 connecting cable    -   23 notches    -   24 fastening unit    -   26 thermoplastic foam top cover, top cover    -   27 matrix top    -   28 matrix bottom    -   29 matrix sides    -   30 scrap matrix    -   31 scrap open cell foam    -   32 scrap closed cell foam    -   33 scrap combination-cell foam    -   37 gas-trapping inserts    -   38 gas bubbles    -   40 floating island    -   42 bedding pocket    -   44 liner holes

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a preferred embodiment of floating island 40 isillustrated that comprises island body 1, wicking cups 2 and shapedliner 3 for preventing the loss of growth medium. Island body 1 ispreferably further comprised of a nonwoven thermosetting orthermoplastic fiber matrix 4 that has central cavity 5 and bottom cutoutholes 6. Wicking cups 2 are preferably comprised of outer layer 7 andcentral portion 8. Central portion 8 is preferably filled with growthmedium that has been formulated to have wicking ability.

An example of a suitable growth medium is BIOMIX® manufactured byFloating Island International of Shepherd, Mont. BIOMIX is a mixturecomprising a hydrophilic polymer foam and a plurality of organicmaterials such as peat and bark.

Outer layer 7 is preferably comprised of thermoplastic polymer foam thathas been manufactured specifically to have a combination of open celland closed cell pore spaces within the polymer material (to comprise acombination-cell foam). The ratio of open to closed cell pores is setduring the manufacturing process so that outer layer 7 has the abilityto wick water via capillary action while retaining growth medium insidecentral portion 8. Shaped liner 3 is preferably comprised ofthermoplastic polymer foam similar in composition to the material ofouter layer 7. Shaped liner 3 preferably fits inside of island body 1,has liner holes 44 in its lower surface and is filled with growth medium9.

Referring to FIG. 2, a side cross-section view of FIG. 1 is presented,showing a floating island 40 after the island parts have been assembledand plants 10 have become established. Wicking cups 2 are preferablyinstalled into island body 1 via bottom cutout holes 6. Shaped liner 3is preferably installed into central cavity 5 of island body 1. Shapedliner 3 is preferably filled with growth medium 9, and plants 10 areshown growing in growth medium 9. In this embodiment, roots 11 of plants10 have grown through bottom of shaped liner 3, but growth medium 9 isretained within the interior of shaped liner 3. Water is transportedupward via capillary action from water body 12 through outer layer 7 andcentral portion 8 of wicking cups 2, as shown by the arrows. This waterthen spreads laterally throughout growth medium 9 that is situationwithin shaped liner 3, and becomes available to plants 10.

FIG. 3 is a side cross-section view of another embodiment of a floatingisland that comprises lost-cost materials. As shown in FIG. 3, islandbody 1 is preferably comprised of matrix 4, pieces of thermoplastic foam13 with a combination of open and closed cells, plants 10 and optionalbedding pocket or cavity 42 filled with bedding mix 14. The pieces ofthermoplastic foam 13 are preferably both buoyant in water and permeableto gases and water. One or more pieces of thermoplastic foam 13 may alsoact as a barrier to prevent particles of bedding mix 14 from fallingthrough the bottom of bedding pocket 42. The pieces of thermoplasticfoam 13 are preferably comprised of materials that are either thread- orsheet-shaped. The pieces of thermoplastic foam 13 are preferablypenetrable by plant roots and can protect the roots from fish grazing ifplaced at the bottom surface of island body 1. Because the pieces ofthermoplastic foam 13 are buoyant, they reduce the need for otherbuoyancy means. They also have a large internal surface area that is maybe colonized by beneficial microbes. In a preferred embodiment, themicrobes that colonize the interior of the pieces of thermoplastic foam13 metabolize excess nutrients in the water and produce gases duringmetabolism. This metabolism has two benefits: water quality is improvedas the nutrients are removed, and the gases provide ongoing buoyancy toisland body 1.

Referring to FIG. 4, another low-cost embodiment of floating island ispresented in which island body 1 is comprised entirely of thermoplasticfoam 13. In this embodiment, island body 1 may be fabricated byinjecting uncured thermoplastic foam into a mold, and allowing it toform a combination of open and closed cells during curing within themold. The ratio of open and closed cells may be varied between differentzones within the island body. For example, some zones may be made morebuoyant by extruding foam with a higher than average percentage ofclosed cells; other zones may be made more hydrophilic by extruding foamwith a higher than average percentage of open cells. The ratio of opento closed cells may be varied by using multiple extrusion devices (withdifferent open/closed cell ratio outputs) simultaneously to make asingle island. Alternately, the ratio of open to closed cells may bevaried by using a single extruder, by varying the operating conditionsof the extrusion process (e.g., by varying the volume and pressure ofthe expansion gas). Also shown are optional bedding pockets 42, whichmay be molded into island body 1 and filled with bedding mix 14. Thisembodiment is well suited for mass production.

Referring to FIG. 5, another low-cost embodiment of floating island 40is presented. In this embodiment, island body 1 is comprised of grasssod layer 17, buoyant matrix material 18 and an optional layer ofnonwoven matrix material 19. The soil within sod layer 17 traps risinggas bubbles that are generated within island body 1, or otherwise areintroduced into island body 1 (e.g., by an aerator). Optional nonwovenmatrix layer 19 provides an extended zone for plant root growth, inwhich the roots are protected from grazing by fish or other animals.This option may be desirable for applications where islands with largeplants are deployed in ponds containing animals that eat the plantroots.

Buoyant matrix layer 18 may be comprised of: (a) thermoplastic polymershapes (threads, sheets, or solid molded piece), which are buoyant, or(b) thermoplastic polymer foam shapes, which are very buoyant, or acombination of (a) and (b). Foam comprises trapped gas bubbles and istherefore more buoyant than shapes made from the same material that donot contain gas bubbles. In addition to providing buoyancy to islandbody 1, buoyant matrix layer 18 traps soil particles, thereby preventingthe loss of soil from sod layer 17.

Referring to FIG. 6, a preferred embodiment of fastening assembly 20 ispresented. In this embodiment, fastening assembly 20 is comprised of twoor more fastening pins 21 and connecting cable 22. Fastening pins 21 arepreferably formed of any suitably stiff and durable material such asaluminum, stainless steel, mild steel, or nylon. Connecting cable 22 ispreferably made from any suitable strong and durable material such asstainless steel cable or nylon rope. This device is preferably used toconnect two or more floating islands 40 together laterally, therebyeffectively forming a large island. Fastening assembly 20 is preferablyinstalled by pushing fastening pin 21 into the side of an island.Notches 23 in pin 21 catch the strands of the matrix material and lockfastening pin 21 into place. Another fastening pin 21 that is part offastening assembly 20 is pushed into a second floating island, therebyattaching the two islands.

Referring to FIG. 7, a preferred embodiment of fastening unit 24 isillustrated. This device may be used to join vertically stacked layersof island body material, to attach additional buoyant units from below,or to attach accessories such as wind powered aerators to the surface offloating island 40. Fastening unit 24 is preferably made from anysuitable stiff and durable material such as aluminum, stainless steel,mild steel or nylon. The device is preferably made so that it can bepushed into island body 1 by either hand pressure or foot pressure.

Referring to FIG. 8, an embodiment of floating island 40 is shown thatcomprises thermoplastic foam top cover 26, which is preferably comprisedof a thermoplastic foam having both open and closed cells. In thisembodiment, island body 1 is preferably comprised of matrix 4 andthermoplastic foam top cover 26. Top cover 26 preferably providessunlight protection to matrix 4 while allowing plants 10 to penetrateit. In this embodiment, top cover 26 is preferably pre-manufactured insheet form and attached to matrix 4 by polymer adhesive or mechanicalfasteners (not shown). Alternately, top cover 26 may be pre-manufacturedin a shaped form to enable it to fit closely over the rounded shape ofthe top of matrix 4, by extruding the uncured foam resin into a shapedmold for curing during the manufacturing process.

Referring to FIG. 9, a preferred embodiment of floating island 40 ispresented that is comprised of a significant percentage of scrapmaterial. In this embodiment, island body 1 is comprised of matrix top27, matrix bottom 28 and matrix sides 29. The interior portion of theisland body 1 is preferably filled with pieces of scrap material thatinclude scrap matrix 30, scrap open cell foam 31, scrap closed cell foam32, and scrap combination-cell foam 33. Additional scrap material ispreferably attached to island body 1 as shown. In this embodiment,buoyancy for the island body 1 is provided by scrap closed cell foam 32and scrap combination-cell foam 33. The pieces of scrap matrix 30 andscrap open cell foam 31 provide a growth medium for the roots of plants10, and they also provide additional surface area for growing beneficialmicrobes.

Referring to FIG. 10, a preferred embodiment of floating island 40 withgas-trapping inserts 37 is presented. In this embodiment, gas-trappinginserts 37 are provided in island body 1. Gas-trapping inserts 37 areinstalled between layers of matrix 4 during the manufacturing operationof island body 1. Gas-trapping inserts 37 may be made in any suitableshape that traps gas, for example, saucer-shaped (as shown) or flatsheets. Gas-trapping inserts 37 are preferably made from a solidthermoplastic or thermoplastic foam. In the case of thermoplastic foam,the foam is preferably made so as to be substantially closed celled inorder to be relatively impermeable to gas. The foam is also preferablymade to be penetrable by plant roots. The foam preferably seals aroundthe root penetration holes so as to provide a relatively gas-tight sealaround the root penetrations. In this embodiment, gas bubbles 38 risethrough gas-permeable matrix 4 until they are blocked by gas-trappinginserts 37. Gas bubbles 38 collect underneath gas-trapping inserts 37and provide buoyancy to island body 1. Gas bubbles 38 may be producednaturally by microbial metabolism within and beneath island body 1, orthey may be produced by mechanical aeration that releases air bubblesbeneath island body 1, or by a combination of these sources.

Many variations of the invention will occur to those skilled in the art.Some variations include a shaped liner and wicking cups. Othervariations call for gas-trapping inserts. All such variations areintended to be within the scope and spirit of the invention.

Although some embodiments are shown to include certain features, theapplicant(s) specifically contemplate that any feature disclosed hereinmay be used together or in combination with any other feature on anyembodiment of the invention. It is also contemplated that any featuremay be specifically excluded from any embodiment of the invention.

1. A floating island comprising: an island body comprising at least twomatrix layers; and a gas-trapping insert that is disposed between saidat least two layers, said gas-trapping insert being fabricated from amaterial selected from the group consisting of a combination-cellthermoplastic foam and a solid thermoplastic; wherein the gas-trappinginsert is in the form of a flat sheet; and wherein bubbles that aregenerated external to the gas-trapping insert are contained underneathit.
 2. A floating island comprising: an island body comprising at leasttwo matrix layers; and a gas-trapping insert that is disposed betweensaid at least two layers, said gas-trapping insert being fabricated froma material selected from the group consisting of a combination-cellthermoplastic foam and a solid thermoplastic; wherein the gas-trappinginsert is in the form of an upside-down saucer; and wherein bubbles thatare generated external to the gas-trapping insert are containedunderneath it.